1. Field of the Invention
The present invention relates to an internal combustion engine control apparatus including a rotation direction detection unit for detecting a rotation direction of a crank shaft of an internal combustion engine.
2. Description of the Related Art
Recently, an idling stop apparatus for performing idling stop control has been proposed for fuel saving and the reduction of CO2 emissions. The idling stop control automatically stops an internal combustion engine (hereinafter, referred to simply as an engine) when a stop condition is satisfied as in the case where the engine is idled and then automatically restarts the engine when a restart condition is satisfied as in the case where a starting operation is performed. Such an idling stop apparatus is required to immediately restart the engine in response to the starting operation or the like.
In view of such a requirement, the following engine starting technique has been proposed. According to the technique, an absolute crank angle of a crank shaft when the engine is stopped is detected to inject a fuel into a specific cylinder (for example, a cylinder on an expansion stroke) in a stop state and to then ignite the fuel. As a result, the energy on combustion immediately starts the engine.
However, when the crank shaft is not in a proper position in the engine stop state, the amount of air in the cylinders is remarkably reduced to prevent sufficient energy on combustion from being obtained or the stroke in which the energy on combustion works on a piston is too short. As a result, there is a possibility that the engine cannot start normally.
In order to solve the above-mentioned problem, a conventional control apparatus for a power train uses a motor generator to rotate a crank shaft to a predetermined position when the crank shaft is not in a proper position in the engine stop state (for example, see Japanese Patent Application Laid-open No. 2001-304080; hereinafter, referred to as Patent Document 1).
It should be noted that if a rotary torque is smaller than a compression force in the vicinity of a compression top dead center when the engine is stopped, a piston sometimes cannot pass the compression top dead center to cause the crank shaft to rotate in the reverse direction. Therefore, in order to accurately detect the stop position of the crank shaft when the engine is stopped, it is necessary to detect the rotation direction of the crank shaft.
However, the conventional apparatus described in Patent Document 1 cited above has a problem in that the stop position of the crank shaft cannot be accurately detected because the rotation direction of the crank shaft is not detected.
Therefore, in order to solve the above-mentioned problem of the conventional apparatus, a conventional rotation detection apparatus includes a rotation direction detection unit having a rotation sensor for detecting a projection provided on a rotary member (crank shaft), an auxiliary sensor for detecting the projection of the rotary member, which is provided at the position offset from the position of the rotation sensor in a circumferential direction, and a processing circuit for determining a forward rotation state or a reverse rotation state of the crank shaft based on outputs from the rotation sensor and the auxiliary sensor to output a rotation direction at a time width of a pulse signal (for example, see Japanese Patent Application Laid-open No. 2005-233622; hereinafter, referred to as Patent Document 2).
In the conventional apparatus described in Patent Document 2 cited above, the rotation direction detection unit detects the rotation direction of the crank shaft based on the outputs from the rotation sensor and the auxiliary sensor.
In the event of a failure in the rotation direction detection unit, it is difficult to accurately detect the stop position of the crank shaft. As a result, there is a possibility that the engine cannot restart. In the event of the wrong recognition of the stop position of the crank shaft, a fuel is injected into a wrong cylinder to be ignited. As a result, there is a possibility that the engine or a suction/exhaust system is damaged by backfire or the like. In order to prevent the above-mentioned problems from occurring, it is necessary to detect an abnormal state of the rotation direction detection unit.
However, since the conventional apparatus described in Patent Document 2 cited above does not detect the abnormal state of the rotation direction detection unit, there is a problem in that engine restart fails or the engine or the suction/exhaustion system is damaged.